一：功能
给定两个集合A，B；计算集合的差集，即计算出那些只包含在A中而不包含在B中的元素。
二：用法
#include <vector>
#include <algorithm>
#include <iostream>int main() {std::vector<int> data1{1, 2, 3, 4, 5, 6};std::vector<int> data2{3, 4, 5};std::vector<int> difference;std::ranges::set_difference(data1, data2,std::back_inserter(difference));for (auto v : difference) {std::cout << v << " ";}std::cout << "\n";//{1, 2, 6}
}
#include <vector>
#include <algorithm>
#include <string>
#include <iostream>struct Labeled {std::string label;int value;
};//如果两个集合中元素相等，且A中元素个数比B的多时，则会返回A中多出的那部分元素。
int main() {auto cmp = [](const auto& l, const auto& r) {return l.value < r.value;};std::vector<Labeled> equal1{{"first_a", 1}, {"first_b", 1}, {"first_c", 1}, {"first_d", 1}};std::vector<Labeled> equal2{{"second_a", 1}, {"second_b", 1}};std::vector<Labeled> equal_difference;std::ranges::set_difference(equal1, equal2,std::back_inserter(equal_difference), cmp);for (auto &[label, value] : equal_difference) {std::cout << "[" << label << " | " << value << "] ";}std::cout << "\n";
}
